Portions of this application have been disclosed in U.S. Disclosure Document No. 445,686 filed with the United States Patent and Trademark Office on Oct. 11, 1998, an entire copy of which is incorporated herein by reference.
1. Field of the Invention
The field of the invention relates to an article of manufacture that is a long lasting rotary drill bit for drilling a hole into variable hardness geological formations that has at least one self-actuating compensation mechanism triggered by bit wear that is responsive to the hardness of the geological formation to minimize the time necessary to drill a borehole using rotary drilling techniques typically used in the oil and gas drilling industries. The field of the invention also relates to a long lasting rotary drill bit for drilling a hole into variable hardness geological formations that has a compensating mechanism controllable from the surface of the earth to change the mechanical configuration of the bit in the well to minimize the time necessary to drill a borehole. The field of invention further relates to an article of manufacture that is a drill bit possessing hard abrasive rods cast into steel, such as tungsten carbide rods cast into steel, that is used to drill holes into geological formations. The field of invention also relates to a composition of matter comprised of tungsten carbide rods cast into relatively softer bit matrix materials, such an alloy steel, to make a self-sharpening drill bit as the bit wears during drilling. The field of invention further relates to the method using the drill bit having tungsten carbide rods cast in steel to drill holes into geological formations that relies upon the progressive exposure of the tungsten carbide rods during the natural wear and erosion of the softer steel alloy matrix material in the drilling bit which results in the self-sharpening of the drill bit. The field of invention further relates to the method of making a long-lasting drill bit comprised of hard abrasive rods cast into steel that is self-sharpening upon the wear of the drill bit during drilling operations. The field of invention further relates to the method of making a long-lasting drill bit by pre-stressing mechanical elements comprising the drill bit that results in the expansion of the drill bit at its bottom during wear of the drill bit thereby producing a constant diameter hole as the bit wears. The field of invention also relates to a method of making the self-sharpening drill bit that relies upon using hardened metal scrapers that become exposed as the bit undergoes lateral wear which tend to produce a constant diameter hole as the bit wears. And finally, the field of invention relates to a method of making the self-sharpening drill bit that relies upon the lateral drill bit wear to uncover and expose new mud channels that results in lateral mud flow which in turn tends to produce a constant diameter hole as the bit undergoes lateral wear.
2. Description of Prior Art
Other than the applications of the inventor previously cited above, at the time of the filing of the application herein, the applicant is unaware of any art in the field that is relevant to the invention.
The rotary drilling industry presently uses the following types of drill bits that are listed in sequence of their relative importance: roller cone bits; diamond bits; and drag bits (please refer to page 1 of the book entitled xe2x80x9cThe Bitxe2x80x9d, Unit 1, Lesson 2, of the xe2x80x9cRotary Drilling Seriesxe2x80x9d, Third Edition, published by the Petroleum Extension Service, Division of Continuing Education, The University of Texas at Austin, Austin, Tex., hereinafter defined as xe2x80x9cRef. 1xe2x80x9d, and an entire copy of xe2x80x9cRef. 1xe2x80x9d is included herein by reference, and furthermore, entire copies of all of the lessons, or volumes, in the entire xe2x80x9cRotary Drilling Seriesxe2x80x9d are also included herein by reference).
The early types of roller cone bits were steel-toothed (milled) bits that are still in general use today (Ref. 1, FIG. 7). The longest lasting generally available variety of roller cone bits are presently the tungsten carbide insert roller cone bits that have sealed, pressure compensated, bearings. Small tungsten carbide inserts are embedded in the rollers that are used to scrape and fracture the formation while the bit rotates under load. However, there are a large number of rapidly moving parts in a tungsten carbide insert roller cone bit, including the bearings, which make it relatively expensive and prone to eventual failure. Further, the small tungsten carbide inserts in such bits eventually tend to fall out of the cones into the well that results in the failure of the bits (Ref. 1, page 21).
Under ideal operational conditions, the diamond bits can last the longest downhole (Ref 1, page 27). Even though the diamond bits can wear, they have no rapidly moving parts such as bearings, ie., they are xe2x80x9cmonolithicxe2x80x9d. For the purposes of this application the definition of xe2x80x9cmonolithicxe2x80x9d shall be defined to be a one piece item that has no rapidly moving parts. (For the purposes herein, the very slow deformation of mechanical parts due to interior stresses or due to mechanical wear shall not classify the part as a xe2x80x9cmoving partxe2x80x9d.) Monolithic structure is a considerable design advantage over the tungsten carbide insert roller cone type bits which have many rapidly moving parts. However, a diamond bit costs 3 to 4 times as much as an equivalent tungsten carbide insert roller cone bit (Ref. 1, page 27). The expense of the diamond bits are a major disadvantage to their routine use.
The earliest drill bits were a form of drag bit (Ref. 1, page 35). Some modern drag bits have replaceable blades. These bits have no moving parts and are relatively inexpensive. These bits are still used today to drill relatively soft geological formations.
All of the above drill bit designs provide for circulation of the mud from the drill string through the drill bit and into the well. Roller cone bits have drilled watercourses in a xe2x80x9cregular bitxe2x80x9d and fluid passageways in a xe2x80x9cjet bitxe2x80x9d (Ref. 1, pages 3-4). Diamond bits have typically xe2x80x9ccross-padxe2x80x9d or xe2x80x9cradial flowxe2x80x9d watercourses (Ref. 1, pages 27-29). Drag bits can have a modified xe2x80x9cjet bitxe2x80x9d type watercourse (Ref. 1, page 36).
When any of the present drill bits are brand new and unused, many of the above drill bit designs provide various methods to minimize xe2x80x9cundergaugingxe2x80x9d wherein a smaller hole is drilled than is desired (Ref. 1, page 19). Sending a fresh bit into an undergauged hole can result in xe2x80x9cjammingxe2x80x9d or other significant problems (Ref. 1, page 1). When the bits are new, many of the various designs provide a relatively controlled inside diameter of the well and also prevent the tool from being stuck or xe2x80x9cjammedxe2x80x9d in the well. The outer teeth on the cones of a roller cone drill bit (xe2x80x9cgauge teethxe2x80x9d or xe2x80x9cgauge cuttersxe2x80x9d) determine the inside diameter of the hole and prevent sticking or jamming of the bit (Ref. 1, pages 8 and 19). The oversize lower portion of the diamond bit determines the inside diameter of the hole and prevents sticking or jamming of the bit. The lower flared taper on the drag bits determine the inside diameter of the hole and prevents sticking or jamming of the bit.
However, as any well is drilled, the roller cone bits, the diamond bits, and the drag bits undergo wear towards the ends of the bit. In this application, the definition of xe2x80x9clongitudinalxe2x80x9d shall mean along the axis of the bitxe2x80x94i.e., in the direction of hole being drilled at any instant. Therefore, the roller cone bits, the diamond bits, and the drag bits all undergo longitudinal wear during drilling operations. As the bit undergoes progressive longitudinal wear, the drill bit becomes dull, and the drilling rate of penetration (feet per hour) slows. The bit can undergo wear to the point that it ultimately fails. Put simply, the roller cone bits, the diamond bits, and the drag bits become progressively duller and wear-out during drilling. The drilling industry instead desires long-lasting, self-sharpening drill bits. In this application the definition of xe2x80x9clong-lastingxe2x80x9d shall mean a drill bit that tends to self-sharpen under use. In this application, the definition of self-sharpen shall mean any drill bit that tends to compensate for longitudinal wear during drilling operations. The roller cone bits, the diamond bits, and the drag bits do not provide intrinsic self correcting means to produce a self-sharpening drill bit as the drill bit undergoes wear. The definition of the term xe2x80x9clongitudinal compensation meansxe2x80x9d shall mean any means that tends to produce a self-sharpening bit as the bit undergoes longitudinal wear. Put simply, the roller cone drill bits, the diamond drill bits, and the drag bits do not provide longitudinal compensation means to compensate for the longitudinal wear of the drill bit during drilling operations.
As any well is drilled, the roller cone bits, the diamond bits, and the drag bits undergo wear on the sides of the bits. In this application, the definition of lateral shall mean the xe2x80x9cside ofxe2x80x9d the bitxe2x80x94i.e., in a plane perpendicular to the direction of hole being drilled at any instant. Therefore, the roller cone bits, the diamond bits, and the drag bits all undergo lateral wear during drilling operations. As a roller cone bit, diamond bit, or drag bit undergoes progressive lateral wear, the bit drills a tapered hole that is undesirable in the industry. The industry instead desires a xe2x80x9cconstant diameter holexe2x80x9d or constant xe2x80x9cgaugexe2x80x9d hole. In this application, the definition of xe2x80x9cgaugexe2x80x9d shall mean the inside diameter of the hole. The roller cone bits, the diamond bits, and the drag bits do not provide intrinsic self correcting means to produce a constant diameter or gauge hole as the bit undergoes lateral wear. The definition of the term xe2x80x9clateral compensation meansxe2x80x9d shall mean any means that tends to produce a constant diameter or gauge hole as the bit undergoes lateral wear. Put simply, the roller cone drill bits, the diamond drill bits, and the drag bits do not provide lateral compensation means to compensate for the lateral wear of the drill bit during drilling operations.
All the various different types of commercially available bits described above wear during drilling activities. All other parameters held constant, as the bits wear during drilling, the worn bits tend to slow the drilling process and the worn bits produce a smaller diameter hole as the bits wear. The industry would prefer a bit that does not become dull with usexe2x80x94ie, that xe2x80x9cself-sharpensxe2x80x9d during drilling. The industry would prefer a bit that produces a constant gauge hole during drilling in spite of any wear on the bit. This application addresses the industry needs for a self-sharpening drill bit that drills relatively constant gauge holes.
An article of manufacture is described herein that combines many advantages of the above basic three types of drilling bits into one new type of drilling bit. Several preferred embodiments of the invention describe a new bit that is a one-piece monolithic structure that has no rapidly moving parts that therefore has the inherent advantages of the diamond bit and of the drag bit. That new bit uses individual tungsten carbide rods cast into steel which provides some of the bottom cutting action of the bit. Such a bit has the cost advantage of tungsten carbide insert roller cone bits in that relatively inexpensive tungsten carbide materials are used for fabrication of the new bit instead of expensive diamonds. Further, the long tungsten rods tend not to fall out of the new drill bit whereas the diamonds can fall out of the diamond bit (Ref. 1, page 35) and the tungsten carbide inserts can fall out of the tungsten carbide insert roller cones (Ref. 1, page 21). Lost tungsten carbide inserts can cause great difficulties during the drilling process (Ref. 1, page 21). Lost diamonds from a diamond bit can cause great problems during drilling (Ref. 1, page 35). Therefore, the fact that the relatively long tungsten carbide rods in the preferred embodiments of the invention herein tend not to become dislodged and tend not to become lost in the well is of considerable economic importance.
The tungsten carbide rods become gradually and progressively exposed on the bottom of the bit as the drill bit wears while drilling the well thereby providing a self-sharpening of the drill bit. The bit wears under the separate influences of the abrasive rock present and the abrasive nature of drilling mud or other drilling fluids. The tungsten carbide rods are eroded at a slower rate than the alloy steel in which it is cast. Broken ends of the tungsten carbide rods can actually speed the drilling process in analogy with certain phenomena observed with tungsten carbide insert roller cone bits (Ref. 1, page 20). Several hardened metal scrapers are also cast into the sides of the new bit that act analogously to the blades of a drag bit which provide some of the wall cutting action. As the steel alloy matrix material of the bit erodes, these hardened metal scrapers become progressively more exposed that results in self-sharpening of the bit.
It is also desirable that the bit produce a constant gauge hole as the bit wears. Various different embodiments of the invention disclose different methods to accomplish this goal. However, many of the different methods rely upon the wear of the bit during drilling to cause physical changes in the drill bit that result in the compensation for lateral bit wear.
A first class of preferred embodiments of the new bit provide for pre-stressed mechanical elements welded together to form the monolithic drill bit which naturally expand radially upon wearing of the welds on the bottom of the new bit resulting in a lower flair, or xe2x80x9cbell shapexe2x80x9d, of the new bit that in turn determines the inside diameter of the well and that prevents sticking of the bit in the well. The rods facing downward in the first class of preferred embodiments provide compensation for longitudinal bit wear and the lower flair provides compensation for lateral bit wear. A second class of preferred embodiments of the new bit provide a single cast unit having tungsten carbide rods, no welds, but extra lateral hardened metal scrapers to compensate for lateral bit wear. A third class of preferred embodiments of the invention provide a single cast unit having tungsten carbide rods, few welds, but that are heat treated so that the bottom of the bit naturally radially expands upon wear that provides compensation for lateral bit wear to provide a relatively constant gauge hole during drilling. A fourth class of preferred embodiments of the invention provide a single cast unit having tungsten carbide rods, few welds, that has relatively lateral facing hardened metal scrapers that become exposed during the natural wear of the bit which tend to produce a constant gauge hole as the bit undergoes lateral wear. A fifth class of preferred embodiments of the invention provides a single cast unit having tungsten carbide rods, few welds, that possess additional mud cavities that upon the natural wear of the bit, open to the well, causing lateral mud flow that produces a relatively constant gauge hole as the bits undergo lateral wear.
The new bit has watercourses similar to those of a diamond bit. The bit herein uses alternatively xe2x80x9ccross-pad flowxe2x80x9d or xe2x80x9cradial flowxe2x80x9d type watercourses discussed earlier.
The fact that the new drill bit can have a large length over diameter ratio, self-sharpens, and produces a relatively constant gauge hole as the bit wears results in a long-lasting drill bit that is of considerable importance to the drilling industry.
Accordingly, an object of the invention is to provide new articles of manufacture that are drill bits used to drill holes into the earth.
It is another object of the invention to provide new articles of manufacture that are drill bits which use tungsten carbide rods cast into steel to produce long-lasting self-sharpening drill bits.
It is yet another object of the invention to provide pre-stressed mechanical elements welded together to form a monolithic drill bit which expand radially in the well producing a flair on the bottom of the bit that determines the inside diameter of the well and that is used to prevent jamming of the bit in the well.
It is another object of the invention to provide a new composition of matter comprised of tungsten carbide rods cast into alloy steel to form a drill bit.
Further, it is another object of the invention to provide new methods of using the drill bit comprised of tungsten carbide rods cast into steel that results in a self-sharpening of the drill bit while the hole is being drilled.
It is yet another object of the invention to provide a method to manufacture long lasting drill bits by casting relatively hard rods into matrix materials such as by casting tungsten carbide rods into alloys of steel.
It is another object of the invention to provide a new composition of matter comprised of tungsten carbide rods cast into steel to form a drill bit that is heat treated to form a monolithic drill bit which, upon wear, naturally expands radially in the well producing a flair on the bottom of the bit that determines the inside of the well and that is used to prevent jamming of the bit in the well.
It is yet another object of the invention to provide a single cast drill bit having tungsten carbide rods cast into steel alloy matrix material, few welds, that has relatively lateral facing hardened metal scrapers that progressively become exposed during the wear of the bit that tend to produce a constant gauge hole as the bit undergoes lateral wear.
It is another object of the invention to provide a single cast drill bit having tungsten carbide rods cast into steel alloy matrix material, few welds, that possesses cavities which upon wear of the bit, open to the well, causing lateral mud flow into the well which in turn produce a constant gauge hole as the bit undergoes lateral bit wear.
It is also another object of the invention to provide a monolithic self-sharpening, long lasting, rotary drill bit having longitudinal compensation means to compensate for the longitudinal wear of the drill bit during drilling operations.
And it is another object of the invention to provide a monolithic rotary drill bit having lateral compensation means to compensate for the lateral wear of the drill bit to provide a bit capable of drilling relatively constant gauge holes during drilling operations.
It is further an object of the invention to provide an article of manufacture that is a long lasting rotary drill bit for drilling a hole into variable hardness geological formations that has at least one self-actuating compensation mechanism triggered by bit wear that is responsive to the hardness of the geological formation to minimize the time necessary to drill a borehole using rotary drilling techniques typically used in the oil and gas drilling industries.
And finally, it is another object of the invention to provide a long lasting rotary drill bit for drilling a hole into variable hardness geological formations that has a compensating mechanism controllable from the surface of the earth to change the mechanical configuration of the bit in the well to minimize the time necessary to drill a borehole.